1. Field of the Invention
The present invention relates to a system, apparatus, method, etc. which verify whether image data generated by an image generation apparatus such as a digital camera has been altered.
2. Related Background Art
Recently, digital cameras which store optical images of subjects by digitizing them have been put into practical use.
Image data created by a digital camera can be captured easily into a personal computer, but at the same time there is the problem that it can be altered easily on the personal computer. Consequently, image data created by a digital camera has the problem that it has lower reliability than silver halide photographs and is not very admissible as evidence. Therefore, digital camera systems have recently been proposed which have a capability to attach a digital signature to image data created by a digital camera. Conventional digital camera systems are disclosed, for example, in U.S. Pat. No. 5,499,294 and Japanese Patent Laid-Open No. 9-200730.
Normally, public-key cryptography such as RSA encryption is used to generate digital signatures. However, the public-key cryptography such as RSA encryption, which involves exponent operations and multiplication/division operations, is not good at high-speed processing and requires hundreds to thousands of times as much processing time as common-key cryptography such as DES. Thus, there is the problem that conventional digital cameras with their limited computational resources have great difficulty in generating digital signatures. Although there is a way to improve the performance of the computational resources of digital signatures extensively so that digital signatures can be generated easily, but this is not desirable because such a method will greatly increase the costs of the digital cameras themselves.